Yaskawa GA700 OC Fault — Overcurrent Fix

What this code means

The Yaskawa GA700 is the latest generation general-purpose inverter, succeeding the A1000 series. The OC fault (Overcurrent) appears when the drive’s output current exceeds 200% of the drive’s rated current. The GA700 has enhanced current detection compared to earlier Yaskawa drives and can distinguish between acceleration overcurrent (oC1), deceleration overcurrent (oC2), and constant-speed overcurrent (oC3), giving you a more precise indication of when in the operating cycle the fault occurs.

OC Sub-Faults on the GA700

Common Causes

• oC1 (During acceleration) — Acceleration time too short for the load inertia, mechanical obstruction (seized bearing, jammed conveyor), or a winding-to-winding short in the motor. Extend the acceleration ramp (parameter C1-01) and verify the load is unobstructed.
• oC2 (During deceleration) — Deceleration time too short for a high-inertia load. The motor is being regenerated too aggressively and the current spikes. Extend the deceleration time (parameter C1-02) or add a dynamic braking resistor/unit.
• oC3 (At constant speed) — A sudden mechanical overload: a pump running against a closed valve, a conveyor carrying a jammed object, a fan blade striking debris. Also caused by motor winding damage or a ground fault.
• Motor cable too long — Long motor cables (over 100 feet) create capacitive charging currents that the drive reads as overcurrent. This is more common on the GA700’s high-frequency carrier (default 2 kHz).
• Incorrect motor parameters — If the motor nameplate data entered in the GA700’s parameter groups (E1-02 through E1-09 for motor ratings) doesn’t match the actual motor, the drive’s overcurrent protection may trigger at the wrong level.

Step-by-Step Fix

1. Note the exact sub-fault code (oC1, oC2, or oC3) — The sub-fault tells you when in the cycle the overcurrent occurs, which directs you to the right fix.
2. For oC1 — Increase the acceleration time in parameter C1-01. Start by doubling the current value. Also verify the load is freely rotating by hand (with power off) before restarting.
3. For oC2 — Increase the deceleration time in parameter C1-02. If the load has very high inertia (large fans, centrifuges), add a dynamic braking unit and resistor to absorb regenerative energy.
4. For oC3 — Check the mechanical load. Remove the obstruction if present. Measure motor phase currents with a clamp meter during steady-state operation — they should be balanced and below nameplate FLA.
5. Megger the motor — With the motor disconnected from the drive and power off, test insulation resistance phase-to-ground (500V DC megger). Values below 1 MΩ indicate deteriorating insulation that will produce intermittent OC faults.
6. Check motor cable length and shielding — If the cable run exceeds 100 feet, add a load reactor (output choke) at the drive output terminals to reduce capacitive charging current.
7. Verify motor parameters — Navigate to the GA700’s E1 parameter group and confirm motor voltage (E1-01), motor rated current (E1-03), motor rated frequency (E1-04), and motor rated speed (E1-05) all match the motor nameplate.
8. Run auto-tune — After confirming motor parameters, run the GA700’s auto-tune function (T1-00 parameter). Auto-tune measures the actual motor characteristics and optimizes the drive’s control performance, which can eliminate OC faults caused by improper vector control tuning.

Parts Often Needed

When to Call a Pro

If oC3 persists with a confirmed healthy motor, correct cable length, and properly tuned drive parameters, the GA700’s IGBT output stage may have developed a fault. Yaskawa’s Technical Support Center (1-800-927-5292) can walk through advanced diagnostics, or the drive can be sent to a Yaskawa authorized repair center for board-level testing.